Night Owls Face 16% Higher Risk of Heart Attack and Stroke

Researchers have found that people who stay up late and are naturally active in the evening face a substantially higher risk of heart disease compared to those who prefer earlier schedules. The findings come from an analysis of health data covering more than 300,000 British adults and represent one of the largest investigations into how sleep timing affects heart health.

The study, published in the Journal of the American Heart Association, tracked participants over roughly 14 years and measured their cardiovascular health using a standardized scoring system that examines eight key factors. The results show that night owls—people who described themselves as definitely evening types—had a 79% higher likelihood of having poor overall heart health scores and faced a 16% increased risk of experiencing a heart attack or stroke during the study period.

Background

Circadian rhythms, the body's natural internal clock, play a significant role in how we sleep and wake. Some people are naturally wired to go to bed early and rise with the sun, while others find themselves most alert late into the evening. Researchers call these patterns chronotypes, and they are largely determined by genetics rather than personal choice.

The study examined three main groups: about 8% of participants identified as definitely evening people, typically going to bed around 2 a.m. and reaching peak activity later in the day. Around 24% described themselves as definitely morning people, who went to bed around 9 p.m. and were most active early in the day. The remaining 67% fell into an intermediate category, showing no strong preference for either schedule.

Previous research has suggested links between irregular sleep patterns and heart disease, but this new investigation provides one of the most comprehensive looks at how chronotype specifically affects cardiovascular health in a large population.

Key Details

When researchers compared night owls to people in the intermediate group, the differences were striking. Evening types showed dramatically worse scores on the American Heart Association's Life's Essential 8 measure, which evaluates both behaviors and health markers. This includes diet quality, physical activity, sleep duration, nicotine exposure, blood pressure, body mass index, blood sugar levels, and blood fat levels.

Morning people, by contrast, showed slightly better outcomes than the intermediate group, with a 5% lower prevalence of poor cardiovascular health scores.

Why the Risk Is Higher

The researchers identified several lifestyle factors that explain much of the elevated risk among night owls. Lead researcher Sina Kianersi from Brigham and Women's Hospital explained the core problem:

"Evening people often experience circadian misalignment, meaning their internal body clock may not match the natural day-to-night light cycle or their typical daily schedules. Evening people may be more likely to have behaviors that can affect cardiovascular health, such as poorer diet quality, smoking and inadequate or irregular sleep."

When researchers analyzed which specific factors contributed most to the higher heart disease risk, they found that nicotine use had the strongest impact, explaining 34% of the increased risk. Shorter sleep duration accounted for 14% of the extra risk. High blood sugar contributed 12%, while body weight and poor diet each explained about 11% of the increased danger.

Notably, about 75% of the higher heart disease risk among night owls could be explained by these lifestyle and health factors rather than sleep timing alone. This suggests that the evening chronotype itself may not be the direct cause of heart problems, but rather that evening types tend to engage in habits that harm their hearts.

Gender Differences

The study revealed important differences between men and women. Women who were night owls showed a 96% higher likelihood of having poor cardiovascular health scores, compared to 67% for men. However, when it came to actual heart attack and stroke risk, the gender difference was less pronounced, with both groups showing the same 16% increased risk.

What This Means

For people who naturally prefer staying up late, the findings are not entirely bad news. Researchers emphasize that the risks are largely tied to behaviors that can be changed. Someone with an evening chronotype is not inherently doomed to heart problems—they simply need to be more intentional about maintaining healthy habits.

Kristen Knutson, a cardiovascular health researcher and chair of the American Heart Association's 2025 statement on circadian health, noted that the findings create a clear opportunity for intervention:

"Evening types aren't inherently less healthy, but they face challenges that make it particularly important for them to maintain a healthy lifestyle. These findings show that the higher heart disease risks among evening types are partly due to modifiable behaviors such as smoking and sleep. Therefore, evening types have options to improve their cardiovascular health."

This means night owls who want to reduce their heart disease risk should focus on quitting smoking if applicable, improving sleep quality and duration, eating a healthier diet, and getting regular physical activity. The specific timing of sleep matters less than ensuring adequate sleep, good nutrition, and avoiding nicotine.

The research also highlights how circadian misalignment—when a person's internal clock conflicts with their daily schedule and environment—can make it harder to maintain healthy habits. Someone who naturally wants to be active at night may struggle to fit into a world built around daytime schedules, making it more difficult to exercise regularly, eat well, or get enough sleep.

For healthcare providers, these findings suggest that understanding a patient's natural sleep preferences could be an important part of cardiovascular risk assessment and prevention strategies. Rather than simply telling patients to go to bed earlier, doctors might help evening types work within their natural rhythms while still addressing the modifiable risk factors that drive up their heart disease risk.